Mark Hinsley sees problems with the infiltration into our countryside of an Eastern oak which falls well below the standards set by its English counterpart.
It is quite fashionable at the moment to be concerned about infiltration into England from South-West Asia and much of the media is full of dark warnings and deep concerns, so, never one to resist a ride on a good band wagon, I need to tell you that there is one major infiltration that is being missed, a group that has been here quite a while softly, softy, taking over our countryside, squeezing out our natives, stealing our women (well, perhaps not the last bit).
What tiny sneaky insidious creature am I talking about, I hear you ask.
I’ll tell you – the tiny sneaky insidious 39 metres tall with a seven-metre girth Quercus cerris – the Turkey oak.
An awful lot of you, gentle readers, despite the fact that picking up a copy of Country Gardener does place you in the horticultural elite, will not know the difference between a Turkey Oak (Quercus cerris) and a native English oak (Quercus robur or Quercus patraea).
The easiest way to recognise a Turkey oak is to take a close look at the twigs as the buds are surrounded by ‘whiskers’ approx 10mm long; the acorn cup has a similarly shaggy appearance and the leaves tend to be more deeply lobed with pointy ends. Also, frequently, it will be big. It grows at a ferocious rate and does make a magnificent specimen tree. They were first recorded in this country growing as an ornamental in 1734 and first recorded as having ‘escaped’ into the wild in the early 1900s.
Compared to our native oaks their timber is rubbish and their wildlife conservation value is low.
One well documented problem with Turkey oak is Andricus quercuscalicus (the knopper gall wasp), which has a dual host life-cycle between Turkey oak and English oak that results in the English oak producing deformed and sterile acorns, thus leaving the field more open for the Turkey oak to colonise. In 1998 the Ministry of Defence, who know a bit about keeping out invaders, ordered all Turkey oak on their land to be removed.
Another, more subtle, problem I read about recently is that Turkey oak acorns contain more tannin, which makes them more durable and less palatable to wildlife. As a consequence, if both species are present in woodland, the English oak acorns will be eaten first, with more of the Turkey oak acorns being buried for winter supplies. Add this to the number of English oak acorns that are already sterile, and you have a pretty effective long-term takeover plan.
There are plenty of Turkey oaks out there that are subject to Tree Preservation Orders, particularly the indiscriminate Area or ‘Blanket’ type. Some local authorities in our area recognise the threat and will allow them to be removed whilst others do not.
We are currently dealing with one that will not allow a mature Turkey oak to be felled that is within 50 metres of a designated woodland wildlife conservation project, despite the fact that young Turkey oaks are already appearing in the woods!
I recently visited an estate in rural West Dorset to undertake a tree safety liability assessment. The countryside was beautiful: rolling hills, fields of sheep, copses and shelterbelts – ‘chocolate box’ Dorset. The client pointed out that the estate was mostly covered with beech and oak.
I looked at the tree closest to me, “But this is a Turkey oak”, I said. “Yes”, answered the client,
“All our oaks are Turkey oaks”.
Rather chilling really – because without a close look, you would not spot the difference.
Mark Hinsley is from Arboriculture Consultants Ltd. www.treeadvice.info